Sensitometer for photoconductive materials

ABSTRACT

SAMPLES OF PHOTOCONDUCTIVE MATERIALS, ARRANGED IN THE FORM OF A CONTINUOUS BELT, ARE SENSITOMETERICALLY TESTED BY SUCCESSIVELY PASSING SUCH SAMPLES PAST ERASE, CHARGE, AND EXPOSE STATIONS. TWO KINDS OF EXPOSURE STATIONS ARE PROVIDED, VIZ ONE IN WHICH THE SAMPLES ARE FLASHED VIA AN OPTICAL WEDGE AND ONE IN WHICH THE SAMPLES ARE RANDOMLY FLASHED FOR THE PURPOSE OF SIMULATING ACTUAL USE FOR THE SAMPLES. THE SAMPLES IN THE PHOTOCONDUCTIVE BELT ARE PERIODICALLY WEDGE FLASHED DURING CERTAIN CYCLES OF THE BELT,   AND RANDOMLY FLASHED DURING OTHER CYCLES. A RECORDER DEVICE, OPERABLE WHILE WEDGE FLASHING, PRODUCES SETS OF V-LOG E RECORDS FOR THE RESPECTIVE CYCLES.

Jan. 23, 1973 G LET-SON E'TAL 3,713,021

SFINSI'I'OME'IER FOR IHO'IOCONDUC'IIVF MATERIALS Filed June 25, 1971 2 Sheets-Sheet l 20 FIG //1 A I iv "(I recorder 7 60 c/ufch GEORGE M LETSON ROBERT WHITMAN JAMES J. 5COTT,JR.

INVENTOR3 ATTORNEY Jan. 23, 1973 G. LET-SON ETAL 3,713,021

SENSI'IOMETER FOR PHOTOCONDUCTIVE MATERIALS 2 Sheets-Sheet 2 Filed June 25, 1971 F l G I5 3X puse /05 rare pc ro paffern f QE? H. l l on pulse gf gen Camparalar I COL/flier clear N T 96 74 H l t Com arafar pulse pc l0 fie/d mefer 51,5 T

l 4 samples in cycle l 1 on off W pu se paflern flasher Comparator 1 gen 88 T I T 72 X 5/05 35 9 recorder 7 V cluich 1 pulse rate pc 10 wedge deficlar l H I l pulse clear Comparafar a counter I I I 7 5 Comparalar L 1 92 decoder 1 pulses in cycle mam} samples 1r; cycle Cycle /66 V Caumer Comparalar counter l 1' I I l clear 84 Camparalor l I I I I T samples in cycle wedge flasher Caunfer 52 A clear 2 GEORGE M. LETSO/V phalo conducflve maferlal ROBERT 2 conducfar Q I nan-conducllve base l 7 A a l BY M 61 7 -I A7- TOR/V5) United States Patent U.S. Cl. 324-32 6 Claims ABSTRACT OF THE DISCLOSURE Samples of photoconductive materials, arranged in the [form of a continuous belt, are sensitometrically tested by successively passing such samples past erase, charge, and expose stations. Two kinds of exposure stations are provided, viz one in which the samples are flashed via an optical wedge and one in which the samples are randomly flashed for the purpose of simulating actual use for the samples. The samples in the photoconductive belt are periodically wedge flashed during certain cycles of the belt; and randomly flashed during other cycles. A recorder device, operable while wedge flashing, produces sets of Vlog E records for the respective cycles.

BACKGROUND OF THE INVENTION Field of the invention This invention relates in general to sensitometers and related equipments. In particular, the invention provides an improved form of sensitometer for checking the qualities of photoconductive materials.

Description relative to the prior art Apparatus for sensitometrically checking photoconductive materials are well known: A photoconductive material under test is charged; optically exposed through a test pattern such as a density wedge; and sensed for charge, thereby to produce and/ or record a Vlog E relationship for the material. U.S. Pat. No. 3,449,658 exemplifies sensitometric apparatus of such type. Although such prior art apparatus may be employed to life-test photoconductive material, by successively recycling such material through the test equipment, the standard for such life-testing leaves something to be desired. It would be desirable, in connection with a sensitometer for photoconductive materials, firstly to simulate sensitometrically the actual usage to which the photoconductive material will be put; and secondly, to life-test sensitometrically such material in relation, not to some arbitrary standard, but rather in relation to other photoconductive material(s) being similarly tested at the same time.

SUMMARY OF THE INVENTION To provide use-simulation, and life-testing in relation to other similarly tested photoconductive materials, the invention proposes that several samples of photoconductive materials to be sensitometrically tested be arranged preferably in the form of a continuous belt; and that the belt be run continuously past an exposure station at which each sample is successively (and periodically) flashed through an exposure wedge. A field meter-and-recorder combinationdisposed after the exposure station and before an erase station for removing the wedge pattern of charge on the samples-registers the Vlog E relationships for the various samples. Each wedge exposure of a sample produces a Vlog E record; and thus, the successive exposures of a given sample produce a set of Vlog E records which indicate the life qualities of such sample in comparison to sets of Vlog E records for the other samples.

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Since actual use of photoconductive material obviously does not entail exposure thereof through a Wedge, the invention proposes to expose (between the times for pcriodic wedge flashing of respective samples) each of the samples to a series of random fiashings, thereby to simulate the way in which such photoconductive material will actually be used. (That is, a different set of charge patterns will be produced on each sample for each random flashing.) To implement such series ocf random flashings, the invention proposes the use of a pattern reticle through which sample flashings obtain, such flashing being slightly out-of-synch with the movement of the sample belt past the random flashing station.

OBJECTS(S) OF THE INVENTION To provide sensitometric evaluation of photoconductive materials by indicating the relative lives of such materials and/ or simulating the use to which such materials will be put.

The invention will be described with reference to the figures, wherein:

FIGS. 1A and 1B are schematic block, diagrams partially in perspective, illustrating an embodiment of the invention, and

@FIG. 2 is a view useful for describing the invention.

With reference to FIG. 1, a set of ten photoconductive samples are arranged in the form of a belt 10. The photoconductive samples comprise photoconductive material atop a conductive layer that is supported on a non-conductive base, the edges of which are in the nature of brushes. See FIG. 2. The lead sample 1 of the belt is provided with an indexing notch 12; and such notch is identified, i.e. read, by means of a lamp-and-photopickup device 14. Charge is placed on the various photoconductive samples of the belt 10 by means of a corona-producing station 16 which is excited by a high voltagesource (not shown), the uncharged side of the belt being electrically grounded by means of rollers 20.

A wedge exposure station 22 includes, within a shroud 23, a flash lamp 24 and a variable density optical wedge 26. The flash lamp 24, as will be described later, is timed to be flashed, during certain cycles of the belt 10, and while the respective photoconductive samples fully occupy the shroud 23.

A field meter 28 measures the charge on the photoconductive samples and feeds its signal output to a recorder 30 of the scribe (32)-and-moving web (34) type. The recorder 30 is, as will be described below, timed to operate-during certain cycles of the belt 10-as soon as the first photoconductive samples reach the field meter 28, and for a duration corresponding to the time it takes for the ten cycles to pass the field meter 28.

The belt 10 of photoconductive samples traverses a random flashing station 31 (which will be described below), pastand in driving relationship with-a rotary pulseproducing device 34 which may be of any Wellknown type. The rotary pulse-producing device 34 is driven by means of a motor 35=Prior to the respective belt samples reaching the indexing lamp-and-photopickup device 14, they are erased of charge by a continuously lit lamp 36 that is housed within a shroud 38, thereby to ready the belt samples for their next charge-and-expose cycle.

During the cycles of the photoconductive belt 10' wherein wedge flashing within the shroud 23 does not obtain, flashing obtains at the random flashing station 31. The random flashing station 31 includes a flash lamp 40 and a pattern reticle 42 within a shroud 44. The flash lamp 40, as will be described below, is timed to flash, during several successive belt cycles, while the respective samples occupy the random flashing station 31, and at a rate that is slightly different than the rate at which the samples pass the station 31. This out-of-synch flashing has the effect of periodically randomly exposing different areas of the belt samples, thereby simulating, in a sensitometer, the way in which the photoconductive samples will be put to actual use. While successive wedge exposures and their resulting sets of Vlog E records are extremely useful in evaluating photoconductive samples, the fact that the invention provides random flashing during certain cycles of the belt means that the Vlog E records are more meaningful because the samples with which they respectively relate have been exposed somewhat in the way in which they will be exposed in actual use.

The shroud 44 dimension L may be modified sizewise with respect to the length of the samples, provided that there is appropriate changing of the flash rate for the lamp 40, eg halving the dimension L while doubling the flash rate for the lamp 40 will provide the desired random flashing. And, while a grid 42 serves as a pattern reticle, such reticle may take a variety of other forms, such as a plate with holes or slits therein.

The sample belt and the corona charging and exposure stations are adapted to be housed in a light-tight cabinet: the shrouds 23, 38, 44 being to prevent their respective sources of radiation from affecting what occurs at other stations within the cabinet. In this connection, light locks (not shown) are provided at the belt entrances and exits of the shrouds.

As noted above, the recorder 30 is adapted to operate during cycles in which wedge flashing occurs: To this end, a signal-responsive clutch 50, the input of which is driven by the motor 35, cooperates through gearing 52 to drive the recording web 34. The gearing 52 is dis posed to cause the recorder web 34 -when the clutch 50 is engagedto go through one cycle for each cycle of the sample belt 10'.

Operation of the apparatus of FIG. 1 will be described with reference to a logic circuit for practicing the teachings of the invention; and to illustrate the basic philosophies of the invention, the belt samples will each be wedge-exposed during the first belt cycle, then randomly flashed, say during the second, third, and fourth belt cycles, then wedge-exposed during the fifth cycle, etc.

As soon as the motor 35 is actuated, the sample belt 10 starts to run the notch 12 to the stop point defined by the lamp-and-photopickup device 14. When the start point is reached, a gate 60 is opened to allow pulses from the rotary pulser 34 to be applied to a counter 62. (And, as the belt samples move up to the start point, they are erased of charge by the continuously lit lamp 36, and prepared, for exposure, by the continuously excited corona-producing device 16.)

The belt 10, during a single cycle thereof, causes the rotary pulser 34 to produce a predetermined number of pulses (and at a rate dependent'on the belt speed). Thus, when the count of the counter 62 reaches the abovementioned predetermined number, a count comparator 64 produces and applies a signal to a cycle counter 66 (and clears and readys the counter 62 for the next belt cycle). The count of the cycle counter 66, therefore, indicates whether the belt is in its first, second, etc., cycle. A decoder matrix 68, appropriately set for the different counts of the cycle counter 66, opens, or not, a pair of gates 70, 72 on the one hand, and a gate 74 on the other hand.

Assume the decoder matrix 68 has been set to produce an output during the first cycle of the belt (i.e. gates 70, 72 are open): When the count of the counter 62 reaches a count corresponding to the belt distance between the start point (lamp and photopickup device 14) and the exit of the wedge flasher 22, a comparator 76 applies, through the open gate 70, a signal to turn on a pulse generator 78. The pulse generator 78 produces pulses, at a rate dependent on the belt speed (detector 80), for wedge flashing each sample once 4 while such samples are respectively within the wedge flashing station 22. The pulse output of the generator 78 is applied to a counter 82 which, after the ten samples in the belt have been flashed, causes a comparator 84 to turn off the pulse generator 78.

When, during the first cycle of the belt 10, the count of the counter 62 reaches a count corresponding to the belt distance from the start point (lamp and photopickup device 14) to the field meter 28, a comparator 86 produces and applies a signal through the opened gate 72 to turn on a pulse generator 88. The pulse generator 88, like the pulse generator 78, produces (detector 89) pulses at a rate dependent on the speed of the sample belt 10. However, rather than use such pulses for flashproducing purposes, they are used instead to define (by means of a counter 90 and comparator 92) when and for how long the counter drive clutch 50 is to be energized. Thus, during the first cycle of the belt 10, the ten web samples are respectively flashed; and the recorder 30 driven through one cycle to register ten corresponding Vlog E records.

During the second (third and fourth) cycle of the belt, the decoder matrix 68, in response to the cycle counter 66, has no output; and attendantly, the gates 70, 72 close, and the gate 74 opens. When the count of the counter 62 has a count corresponding to the belt distance between the start point and (in this embodiment of the invention) the exit of the random flashing station 31, a comparator 96 produces and applies, through the opened gate 74, a signal to a pulse generator 98. The pulse generator 98 produces-in response to a biased detector 100-pulses slightly out-of-synch with the passage of samples past the random flashing station 31. By means of such outof-synch pulses, the pattern reticle 42 is flashed onto each given sample of the belt slightly differently during the second belt cycle (and slightly differently during the third and fourth belt cycles), thereby simulating the actual use to which the belt samples will be put. (To be borne in mind is that during the simulation phase of the operation of the sensitometer of FIG. 1, Vlog E records are not not made by the recorder 30.)

During the fifth belt cycle, i.e. when the decoder matrix 68 again produces an output, wedge flashing of the ten samples, to produce a corresponding second set of Vlog E records, resumes; followed by random flashing during the sixth, seventh, and eighth belt cycles, etc.

Summarizing, the invention teaches, in a sensitometer for photoconductive material, the use of a continuous moving belt of photoconductive samples, whereby-With the aid of a recordertheir respective qualities can be checked with respect to each other; and wherein by periodically randomly flashing such samples-say by means of out-of-synch flashing through a pattern reticleactual-use simulation will obtain for such samples.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that 'variations and modifications can be effected within the spirit and scope of the invention. For example, other recording devices (e.g. a storage CRT) or logic techniques may be employed without departing from the invention. Also, various other functions can be performed during certain cycles for the sample belt 10, such, for example, as registering charge levels without flashing; or registering charge levels after erasure; etc.

What is claimed is:

1. Apparatus for checking the sensitometric qualities of a plurality of samples of photoconductive samples arranged in the form of a continuous belt, comprising:

(a) means for conveying said continuous belt of samples past a plurality of stations about the periphery of said belt,

(b) means at a first of said stations in the direction of belt travel for erasing charge from the samples in said belt,

() means, at a second station following said first station in the direction of belt travel, for applying charge to the samples in said belt,

(d) means, at a third station following said second station in the direction of belt travel, for exposing said samples to an optical test image,

(e) means, at a fourth station following said third station in the direction of belt travel, for measuring and recording the charge on respective ones of said samples,

(f) means, at a station in the direction of belt travel which is after said charge applying means and before said charge erasing means, for applying random exposures to said samples, and

(g) control means for periodically enabling said means for applying random exposures to said samples, and for disabling said means for measuring and recording charges on said samples while said random exposure means is enabled.

2. The apparatus of claim 1 wherein said control means includes means for disabling said means for exposing said samples to an optical test image when said recording means is disabled.

3. The apparatus of claim 1 wherein said random exposing means includes a pattern reticle and means for flashing said samples through said reticle, and wherein said apparatus includes means for actuating said flashing means out of synchronism with the passage of said samples past said random exposing means.

4. The apparatus of claim 2. wherein said random exposing means includes a pattern reticle and means for flashing said samples through said reticle, and wherein said apparatus includes means for actuating said flashing means out of synchronism with the passage of said samples past said random exposing means.

5. The apparatus of claim 2,

'(a) wherein said means for exposing said samples to an optical test image includes first flash means, and wherein said apparatus includes means for actuating said first flash means in synchronism with the passage of samples past said means for exposing said samples to an optical test image, and

(b) wherein said random exposing means includes a pattern reticle and second flash means for flashing said samples through said reticle, and wherein said apparatus includes means for actuating said second flash means out of synchronism with the passage of said samples past said random exposing means.

6. Apparatus for checking the sensitometric qualities of a plurality of samples of photoconductive samples arranged in the form of a continuous belt, comprising:

(a) means for conveying said continuous belt of samples past a plurality of stations about the periphery of said belt,

(b) means at a first of said stations in the direction of belt travel for erasing charge from the samples in said belt,

(0) means, at a second station following said first station in the direction of belt travel, for applying charge to the samples in said belt,

(d) means, at a third station following said second station in the direction of belt travel, for exposing said samples to an optical test image,

(e) means, at a fourth station following said third station in the direction of belt travel, for measuring and recording the charge on respective ones of said samples,

said recorder of said measuring and recording means he ing of the scribe and continuous web type; and said apparatus including means for running said recording web in synchronism with the conveyance of said continuous belt of photoconductive samples past said stations, and:

(a) means, at a station in the direction of belt travel which is after said charge applying means and before said charge erasing means, for applying random exposures to said samples, and

(13) control means for periodically enabling said means for applying random exposures to said samples, and for disabling said means for measuring and recording charges on said samples while said random exposure means is enabled.

References Cited UNITED STATES P'ATENTS RUDOLPH V. ROLINEC, Primary Examiner E. F. KARLSEN, Assistant Examiner US. Cl. X.R. 

